Where St. Patrick Catholic Church stands today, farmland and groves stood in the 1880s. New Catholic Churches began springing up in neighboring counties. Largo had not grown as rapidly as much of the rest of Pinellas County, but by the mid-1950s, things began to change with industrial plants moving into the area.

In 1957, Archbishop Joseph P. Hurley of the Diocese of St. Augustine, was informed that Catholic growth was taking place in Largo. Unfortunately, they were being forced to attend Mass in Clearwater and Indian Rocks Beach, as those were the nearest churches. As a result, Fr. Scully, Administrator of Sacred Heart Catholic Church in Pinellas Park, was given the task of opening an ‘outpost’ mission in Largo. The first Mass was celebrated on January 9, 1958, at the old Largo Theatre in downtown Largo on West Bay Drive, which was owned by a local Catholic business leader, Henry Glover. Within a few weeks, new arrangements needed to be made, as the Theatre was unable to hold the number of people attending Mass.

In 1958, large tracts of land that once held orange groves became available for purchase. A section of this property was sold to the Diocese in 1958, and on June 7, 1958, a Decree of Erection was signed. Fr. Scully was named Administrator, and Fr. John McCall was named assistant. On March 12, 1960, Fr. John McNulty celebrated Sunday Mass in what is now St. Patrick Catholic Church.